How to elegantly symbolize_keys for a 'nested' hash

There are a few ways to do this

1. There's a deep_symbolize_keys method in Rails

   hash.deep_symbolize_keys!

2. As mentioned by @chrisgeeq, there is a deep_transform_keys method that's available from Rails 4.

   hash.deep_transform_keys(&:to_sym)

   There is also a bang ! version to replace the existing object.

3. There is another method called with_indifferent_access. This allows you to access a hash with either a string or a symbol like how params are in the controller. This method doesn't have a bang counterpart.

   hash = hash.with_indifferent_access

4. The last one is using JSON.parse. I personally don't like this because you're doing 2 transformations - hash to json then json to hash.

   JSON.parse(JSON[h], symbolize_names: true)

UPDATE:

16/01/19 - add more options and note deprecation of deep_symbolize_keys

19/04/12 - remove deprecated note. only the implementation used in the method is deprecated, not the method itself.

You cannot use this method for params or any other instance of ActionController::Parameters any more, because deep_symbolize_keys method is deprecated in Rails 5.0+ due to security reasons and will be removed in Rails 5.1+ as ActionController::Parameters no longer inherits from Hash

So this approach by @Uri Agassi seems to be the universal one.

JSON.parse(JSON[h], symbolize_names: true)

---

However, Rails Hash object still does have it.

So options are:

• if you don't use Rails or just don't care:

  JSON.parse(JSON[h], symbolize_names: true)
  

• with Rails and ActionController::Parameters:

  params.to_unsafe_h.deep_symbolize_keys
  

• with Rails and plain Hash

  h.deep_symbolize_keys